Fitting for duralumin constructions



Patented July 8, 1924 FITTING FOR DURALUMHI GONSTRUCTIONS,

No Drawing.

To all whom it may concern Be it known that I, ADOLF ROHRBACH, a citizen of the German Reich, residing at Charlottenburg, Germany, have invented certain new and useful Improvements in Fittings for Duralumin Constructions, of which the followin is a specification.

A very great di culty in the duralumin construction Work for airplanes, motor boats, or other purposes, is due to the fact that duralumin easily corrodes by the effect of electrolysis. It stands to reason that the duralumin is always destroyed in the neighbourhood of fitting parts, if the electric current passes from the duralumin to the metal of the fittings as this is the case, for instance, in the combination duraluminbronze. A way out of this diificulty has been tried by making the fittings for duralumin constructions of iron, because the electric current passes from the iron .to the duralumin; the iron fittings, therefore, rust easily and severely, but the duralumin, although much more sensitive in itself, remains unhurt. Such iron fittings. have proved to be rather serviceable for land (planes and wherever the fittings were not permanently exposed to the influence of water. But the severe rusting of such iron parts presents serious difficulties, if the fittings are em-.

ployed for sea planes, motor boats, etc. Matters are not much improved, if instead of iron, a non-corrosive steel is used, because such steel contains considerable parts of chrome and nickel. Both these metals together with duralumin constitute a con tact-series, wherein the electric current passes from duralumin to nickel, or chrome respectively, causing also in this case the rather rapid destruction of the duralumin.

To avoid this difliculty, the idea resents itself, to construct the fittings entirely of duralumin. But while such fittings would be extremely difiicult to manufacture and, consequently, very expensive, there would still remain the other unpleasant fact that in this way only another part would be Application filed March 20,.l924. Serial No. 700,618.

exposed to the danger of corroding, if, for instance, the fittings would be attached to' steel tube struts.

Contrary to this, the danger of a corrosion can be entirely eliminated by manufacturing the fittings in the hitherto usual manner of steel or iron, and then protecting them against corrosion by a surface of zinc metal. Smce the voltage between iron and zinc causes the current to pass from zinc to iron, the zinc corrodes, while the iron remains unhurt. 1 The zinc surface is preferably applied in such manner that to the fitting a small piece of zinc is attached which, by

means of a bolt, may be easily removed.

In this way, the zinc, if too much affected, can without difiiculty be replaced by a new piece. This method gives the advantage over the frequently employed zinc-coating of iron fittings that a permanentprotection of the fittings is ensured, whereas the zinc skin of the coated fitting is easily damaged in the course of construction or, with the use of the craft. The electric corrosion which then sets in, destroys within a short time the entire zinc coat, thus leaving the iron fitting to the destructive work done by the influence of duralumin.

I claim:

1. Fittings, or the like, attached to duralumin, to be employed in 'the construction of aircraft etc., wherein the metals .which are in contact with each other, are separated from each other by an intermediate layer of such metal that the generated electric current has a destructive efl'ectupon the interposed plate.

2. Fittings, or the like, attached to duralumin, as described in claim 1, wherein the intermediate layer is easily detachable and interchangeable.

In testimony whereof I afiix my signature in the presence of two witnesses.

DR. ADOLF ROHRBACH.

Witnesses:

WLAD. ENDERS, E. HOLTZERMAIN. 

